1. Field of the Invention
The present invention relates to a keyswitch for use in a keyboard device, and more particularly, to a keyswitch having a keytop that is upwardly and downwardly movable. In addition, the present invention relates to a method of assembling the keyswitch.
2. Description of the Related Art
In recent years, keyswitches suitable for use in keyboard input devices have been proposed in which the top ends of a pair of lever members linked so as to cross each other are supported at a keytop, and, with the upward and downward movement of the keytop, the angle at which the pair of lever members cross each other is changed.
For example, there has been disclosed a keyswitch having a structure in which one of the lever members (the lever member whose top end rotatably engages the back surface of a keytop) and the other lever member (the lever member whose top end slidably engages the back surface of the key top) are linked at a portion where they cross each other so as to be formed into an integral structure, and the integrally formed pair of lever members guide the upward and downward movement of the keytop.
This type of keyswitch is turned on in the following manner. When an operator pushes the keytop, the pair of lever members are tilted and pushed downward. When the keytop has moved downward by a predetermined amount, an elastic member, such as a click rubber, is pushed by the keytop and deformed, after which a switch element of, for example, a membrane switch, is pushed by the elastic member to thereby turn on the keyswitch.
When the pushing operational force on the keytop is removed, the deformed elastic member is restored to its original shape due to its own resilient force, thereby bringing the membrane switch into an OFF state, and simultaneously pushing the keytop up to its initial height while causing the tilted pair of lever members to stand upright.
Accordingly, as compared to a conventional keyswitch whose key stem is slid along a guide wall, the structure in which a keytop is supported by a pair of lever members so as to be movable up and down achieves an ease of operation and a reduction in the height of the keyswitch.
In such a keyswitch, the membrane switch is placed on a metal plate, and portions of the metal plate are cut upward to form engaging portions. Bottom ends of the pair of combined lever members engage their corresponding engaging portions for assembly, whereby the top ends of the pair of combined lever members are movable upward and downward.
However, the keytop used in this type of conventional keyswitch is formed thin in order to make the keyswitch thin. In addition, a rotation engaging section and a slide engaging section are integrally formed at the back surface of the thin keytop in order to rotatably and slidably engage the top ends of the pair of lever members.
The shapes of the rotation engaging section and the slide engaging section are complicated. Thus, the shape of the keytop is likewise complicated. Therefore, the structure of a molding die used to form the keytop (by molding) becomes complicated, thereby resulting in an increase in the cost of the keytop.
In addition, since the rotation engaging section and the slide engaging section of the keytop are formed at the back surface of the keytop by molding, the assembly operation of engaging the top ends of the pair of lever members with the rotation engaging section and the slide engaging section of the keytop, respectively, becomes complicated, thereby making it difficult to automate the assembly operation.
This type of conventional keyswitch is assembled by engaging the bottom ends of the pair of combined lever members with the corresponding engaging portions formed by cutting up portions of the metal plate. However, since the bottom ends of the pair of lever members are mounted to the engaging portions after the membrane switch is placed on the metal plate, the sheet-shaped membrane switch becomes wavy or the like, thereby making it difficult to perform the assembly operation of engaging the pair of lever members with the engaging portions of the metal plate.
Accordingly, in view of the first two problems, it is an object of the present invention to provide a keyswitch that can be reduced in cost by forming a plate-shaped actuator having a rotation connecting section and a slide connecting section with which top ends of a pair of lever members engage. The actuator is formed separately from the keytop, and is mounted by press-fitting it to the keytop.
In view of the third problem, it is an object of the present invention to provide a keyswitch which can be easily assembled, and whose assembly operation is easily automated by placing a lever mounting plate on the membrane switch, which is provided separately from the metal plate, and with which bottom ends of a pair of lever members engage. In addition, it is an object of the present invention to provide a method of assembling the keyswitch.
To these ends, according to a first aspect of the present invention, there is provided a keyswitch comprising a pair of lever members which are rotatably linked at a portion where the lever members cross each other, a keytop supported by the pair of lever members so as to be upwardly and downwardly movable, an elastic member for elastically biasing the keytop upwardly, and a switch element which is subject to a switching operation with the upward and downward movement of the keytop. An actuator, with which the top ends of the pair of lever members are engageable, is disposed in the keytop. In addition, the keytop is held by the actuator. Further, the elastic member directly elastically biases the keytop. Still further, with the upward and downward movement of the keytop, the pair of lever members are upwardly and downwardly movable through the actuator.
In a first form of the first aspect, a prismatic protrusion is formed at a portion of the keytop that is stopped by the actuator, and side surfaces formed at a periphery of the prismatic protrusion are formed flat. In addition, the actuator has a dislodging preventing stopper portion capable of preventing the actuator from becoming dislodged by being press-contacted to the side surfaces at the periphery of the protrusion, a plurality of press-contact portions supported in a cantilever manner being provided at the dislodging-preventing stopper portion, and the press-contact portions being press-contacted to the corresponding side surfaces at the protrusion so that the keytop will be held by the actuator.
In a second form based upon the first form, the press-contact portions are formed so as to be supported in the cantilever manner by causing the press-contact portions to protrude inwardly from an inner peripheral wall defining a hole which passes through the actuator, and ends of the press-contact portions are such as to press-contact the corresponding side surfaces at the protrusion.
In a third form based upon the second form, the actuator is formed of a metallic plate, and the press-contact portions are formed so as to protrude inwardly from four directions of the inner peripheral wall defining the hole. In addition, the keytop is formed of a resin material, and the prismatic protrusion has the shape of a square pole. Further, the press-contact portions are press-fitted to the corresponding four side surfaces at the periphery of the square-pole-shaped protrusion.
In a fourth form based upon the third form, the square-pole-shaped protrusion has a cross-shaped presser portion formed so as to protrude in a diagonal direction from a corner where the side surfaces intersect each other, the length of the presser portion in the diagonal direction being greater than the size of a top portion of the elastic member, and the presser portion being brought into contact with the top portion of the elastic member in order for the elastic member to elastically bias the keytop.
According to a second aspect of the present invention, there is provided a keyswitch comprising a pair of lever members which are rotatably linked at a portion where the lever members cross each other, a keytop supported by the pair of lever members so as to be upwardly and downwardly movable, an elastic member for elastically biasing the keytop upwardly, and a switch element which is subject to a switching operation with the upward and downward movement of the keytop. A lever mounting plate, with which bottom ends of the pair of lever members are engageable, is mounted to a holding plate and is placed on the switch element. In addition, the lever mounting plate includes a rotation engaging section and a slide engaging section. The rotation engaging section has an open portion and allows the bottom end of one of the lever members to rotatably engage therewith. The slide engaging section has an open portion and allows the bottom end of the other lever member to slidably engage therewith. The open portion of the rotation engaging section and the open portion of the slide engaging section open in the same direction.
In one form of the second aspect of the present invention, the lever mounting plate is a metallic plate. The lever mounting plate has a pair of first cut-up portions at one side thereof. In addition, the slide engaging section which has the open portion is formed into a U shape at the first cut-up portions, and two opposing sides of the U-shaped slide engaging section are formed parallel to each other.
In another form of the second aspect of the present invention, a pair of second cut-up portions are formed at the other side of the lever mounting plate so as to be separated from the first cut-up portions, the rotation engaging section being formed into a U shape at the second cut-up portions, and a protrusion being formed near the open portion at either one of or both opposing sides of the rotation engaging section, the protrusion being provided to reduce the width of the open portion.
According to a third aspect of the present invention, there is provided a method of assembling a keyswitch, wherein a pair of lever members which are rotatably linked at a portion where the lever members cross each other are provided; wherein top ends of the pair of lever members are made upwardly and downwardly movable through an actuator with the upward and downward movement of a keytop, which is elastically biased by an elastic member; wherein bottom ends of the pair of lever members are made engageable with a lever mounting plate; wherein the bottom ends of the pair of lever members are positioned on the lever mounting member, the pair of lever members are moved from one side to the other, and the bottom ends of the pair of lever members are made to engage the lever mounting plate in order to assemble the keyswitch.
In a form of the third aspect of the present invention, by moving the pair of lever members from one side to the other, the bottom end of one of the lever members engages a rotation engaging section of the lever mounting plate by a snap-in operation so that the one of the lever members is rotatable thereat, and the bottom end of the other lever member is slid to engage a slide engaging section of the lever mounting plate so that the other lever member is slidable thereat.